I take it DMA is already on and it has been working fine the past week with the same media hmm....
The problems you describe have been reported by other owners here before but in some cases it was the drive that was faulty out of the box and for some it was a configuration error.
So all I can suggest is try a few of the following;
Uninstall the writer from the device manager and let windows reinstall it.
Re-flash B7P9 firmware to the drive.
Double check DMA is turned on in windows and in the bios.
Reinstall chipset drivers but not IDE drivers for NV or VIA chipsets .
(roll back to the MS ones)
Check the IDE connection and cable & try replacing it with another cable.
If you can test the writer in another computer with the same media to see if the problem persists if it does its most likely the drive is defective.
Try installing the adaptec ASPI layer.
Run memtest to check your computers RAM (a long shot but no harm trying)
Clear the motherboards bios and setup again or try flashing the latest bios to it.
I hope one of those helps cause that is a weird one for it to just stop working like that..